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View Full Version : Noise Reduction Techniques?



artem
11-28-2012, 04:50 PM
Hello Everyone,

I've working on an indoor scene and I've been running into noise on my images, even after 10000 passes.

I was wondering if we could have a discussion about ways to reduce said noise and get a nice smooth picture.

To get the discussion going, here are some tricks I tried:

1) Replace emissives material applied to a Lightbulb model with Lights from the Pro version. Result: This did indeed have a slight impact on the quality of the render but the noise is still there.

2) Add an outside light shining in. I've read on a couple of blogs that shadows are tricky for the VRAY engine and so I've added a light coming from the outside of the model into it to add a bit more light. Result: Fail. Did not see a reduction of noise.

3) Generate 3-4 images to overlay in photoshop. Result: Fail. I get the same noise in the same spot everytime. Is there a way to randomize the "seed" of the noise?

Any thoughts?

blitz
11-28-2012, 05:03 PM
Two main observations I've made in how to reduce noise...

1. Use larger emmissives as opposed to small. In some cases this is not possible.

2. Minimize glossy or reflective surfaces.

andy
11-28-2012, 06:52 PM
One thing that can help quite a bit is to avoid white or color values that are at 100%. Keep the numbers all under 240 and you should notice a reduction in noise. Using textures? Use the same trick there.

"small" emissives is really just relative to the scene also. It's because of that I wish there were a few more light shapes and parameters available. There's not much you can do about some of them though.

If you're in a pinch then do a couple partial renders. Light the whole thing without the ceiling. I recommend just making an hdr that pretty much matches your ceiling color for that. Then hide the floor and throw a nice big light to light the ceiling how it should look. Blend those images together in photoshop. That'll help if you need something faster and if having things photochopped is acceptable.

I've only had to do that once. But if anyone figures out how to get reasonable render time on a small white room with a charcoal carpet floor lit in iRay let me know. I don't think it's possible to do it in one shot. I had to do it in Max because my scene was too big for bunkspeed to handle, but I still used iRay. It was a pain in the butt.

david.randle
11-28-2012, 07:22 PM
All the tips that have been shared are on the right track.

Larger surfaces with emissives are easier to sample and therefore reduce noise. Color values on materials and textures below 240 is also a good idea. reducing Glossy surfaces or surfaces with very low levels of roughness will also help.

To be honest though, the easiest thing to do, is apply the "noise removal" filter in Photoshop. Works like a charm.

haknslash
11-28-2012, 07:58 PM
+1 for noise removal in PS. Quickest and easiest method.

artem
11-28-2012, 09:20 PM
I want to give the Reduce Noise filter a shot. How do you guys line up the settings?

haknslash
11-28-2012, 10:18 PM
Not sure what you mean by line up the settings. Really depends on the particular view, lighting conditions and amount of noise. You'll definitely want to use the marquee selection tools to isolate your noise areas. Otherwise the filter will affect the entire image which can wash out colors or soften edges based on the values you enter on the filter dialog box.

Using DoF in Shot will not only create realism but also help with noise in post process. ;)